We propose the first comprehensive evaluation of the intestinal microbiota in premature infants at risk for necrotizing enterocolitis (NEC). The overall goals respond to objectives of the NIH Funding Opportunity Announcement, which include: 1. gaining a better understanding of the bacterial ecology of the infant intestine, 2. understanding how commensal organisms work to dampen inappropriate inflammatory responses of the enterocyte, 3. find methods to better identify prematurely born infants at highest risk of NEC in order to enter them into clinical trials of preventive therapy. Three hypotheses will be tested: Hypothesis 1. Infants who subsequently develop NEC establish a high risk microbiota that can be distinguished from a low risk pattern. This will be accomplished using unique newly developed molecular techniques; Hypothesis 2. High-risk- for- NEC stool microbiota patterns are associated with altered inflammatory mediator markers. This will be evaluated using correlations with plasma samples as well as buccal smears, which may offer the potential for determination of early biomarkers using a relatively non-invasive approach; Hypothesis 3. The high risk fecal microbiota and inflammatory patterns are associated with other morbidities such as hospital acquired sepsis, chronic lung disease and neurological injury. Here we will correlate intestinal microbial patterns and inflammatory marker patterns with non intestinal diseases associated with inflammatory processes in the neonate such hospital acquired sepsis, chronic lung disease and neurologic damage such as intracranial hemorrhage (IVH) and periventricular leukomalacia (PVL). This research will provide new information on the relationship between intestinal microbiota, gut derived systemic inflammation, NEC and other neonatal morbidities. Significance: At the completion of this project a relationship between NEC and stool microbiota will be found: This may consist of finding an individual causative pathogen or more likely, a quantitative or qualitative pattern that is consistently associated with the presence or absence of NEC. This will guide us in the choice of safe and effective preventative measures, such as choice of correct probiotic. In addition, finding inflammation-related markers using a non-invasive technique such as fecal analysis or tongue scraping to determine individuals at highest risk for the development of NEC will improve our chances of only using this preventative therapy for those individuals at highest risk for the disease PUBLIC HEALTH REVELANCE: The relevance of this research is that at the completion of this project a relationship between NEC, one of the most devastating diseases seen in premature infants, and stool microbes will be found: This may consist of finding an individual causative pathogen or more likely, a quantitative or qualitative pattern that is consistently associated with the presence or absence of NEC. This will guide us in the choice of safe and effective preventative measures and result in an enhanced ability to find those at highest risk by use of non-invasive techniques such as fecal analysis or tongue swabs, rather than the more invasive and painful blood based analysis.